Wynn-Williams was born on 10 August 1911 at Middlesbrough, the son of William, a general practitioner and his wife Jane Anderson, née Brymer. He was educated at Rossall School and King's College London, where he won the Hughes prize for anatomy and Chadwick prize for clinical surgery, before completing his medical studies at the Westminster Hospital, where he was taught by Sir Adolf Abrahams. Specialising in obstetrics and gynaecology, he was successively obstetrics and gynaecology tutor at Westminster Hospital, senior registrar at Queen Charlotte's Hospital and obstetric surgeon there. He was also surgeon to the Chelsea Hospital for Women and teacher in gynaecology and obstetrics at London University, and consultant gynaecologist at the Weir Hospital, London. He was the co-author in 1968 of Queen Charlotte's Textbook of Obstetrics. In the second world war he was an EMS Grade 1 surgeon 1941-45, and surgeon in charge of the mobile surgical team, Portsmouth and Southampton from June to October 1944. He was a keen sportsman, playing for the Westminster Hospital's first teams at rugger and hockey, both of which games he played for United Hospitals. As a schoolboy he had played rugger for the north schools against the south. On 20 November 1943 he married Lady Penelope, daughter of the 1st Earl Jowitt of Stevenage, Lord Chancellor 1947-55. They had two sons, William and Hugo, and a daughter, Lesley-Jane. He died on 29 April 1993 survived by his wife and family. A service of thanksgiving for his life was held at All Saints, Fulham on 10 June 1993.